This invention relates to atomizing pump dispensers in general, and more particularly to an improved flat-top valve member particularly useful in a prepressurized type atomizing pump dispenser.
With the advent of restrictions against the use of fluorocarbons in atomizing dispensers and the concern for the effects of fluorocarbons on the ozone layer, the development of pumps which can atomize with the type of fine spray previously obtainable only with a pressurized container has become increasingly important.
The most common proposal for providing good atomizing in a pump comprises carrying out some type of a pre-pressurization. A number of different prepressurized pumps have been developed which include an outlet valve arrangement which does not operate until a certain amount of pressure builds up in a pump chamber so that a fine atomization without dribble can be accomplished. Typical of such pumps are the pumps described in U.S. Pat. No. 4,025,046; U.S. Pat. No. 3,399,836; U.S. Pat. No. 4,089,442 and French patent No. 2,249,716.
Each of the pumps disclosed in the aforementioned patents include a pump chamber in which there is disposed, for reciprocal motion, a piston having a stem integral therewith. The piston contains a central axial bore at the inner end of which there is disposed a valve member which maintains an inlet port to that bore closed until pressure builds up in the pump chamber due to an inward depression of the pump stem. Each of the pumps also includes biasing means, typically a spring, which holds the valve member against the port until a sufficient differential pressure builds up to move it away from the inlet port. All of these pumps also include a valve means at the inlet to the pump chamber. The purpose of the valve means is to permit refilling of the pump during an outward stroke, but to prevent backflow of the material from the pump chamber during a dispensing stroke. The most common manner of achieving the inlet valve is by means of a check valve. Thus, Pechstein, in U.S. Pat. No. 3,399,836, utilizes a ball check valve for this purpose. In French patent No. 2,249,716, the check valve is in the form of a rubber gasket disposed about an extension of the valve member and retained by a plastic cover. When the pump is operated, the pressure developed therein slides the gasket on the stem inward sealing against an opening at the inner end of the pump chamber. After dispensing, the pressure differential, due to the partial vacuum which is drawn inside the pump chamber, results in the gasket being moved upward to open a path for refilling.
In U.S. Pat. No. 4,089,442, a different type of check valve is utilized. The valve member which seals against the inlet port in the dispensing stem has a hollow portion which extends through a throat at the inner end of the pump chamber. Within this hollow section, a spring is disposed and the hollow section is placed in communication with the container. The hollow section is of a larger diameter than the rest of the valve member, being narrowed down at a point below the inlet port into the dispensing stem. This permits openings to be formed from the hollow side of the valve member. When pressure is developed in the chamber, it is pushed inward closing off the openings. When a differential pressure exists, it is pushed upward to permit fluid to flow through the hollow portion of the valve member, the openings and into the chamber.
Another device using a conventional ball check is that of U.S. Pat. No. 4,051,983. In the embodiment disclosed therein, what is therein referred to as the valve member and which both acts to seal at the inner end of the pump chamber and to seal off the inlet port to the dispensing stem, is made of three pieces. There is an upper portion which extends into an opening in the piston and dispensing stem assembly to form, with the inlet port to the dispensing stem, a valve. This part has a hollow portion at its inner end. The hollow portion has a plurality of openings formed therein, and retains a ball. To hold the ball in place a third part is inserted into the hollow portion forming an extension of the valve member. This part carries out the necessary sealing in the inner end of the pump chamber.
The aforementioned U.S. Pat. No. 4,025,046, particularly in the embodiment shown in FIG. 4, dispense without the need for a separate inlet valve using instead cooperation between the valve member and a throat formed at the inner end of the pump chamber. The valve member is constructed so that when the pump is in its at-rest position with the valve member, piston and dispensing stem all fully outward, the valve member, either by means of appropriate channels, tapering or sizing, opens up a path of communication between the container and the pump chamber. This was first disclosed and claimed in U.S. Pat. No. 4,113,145, granted to Philip Meshberg on Sept. 12, 1978, being an improvement on his earlier U.S. Pat. No. 3,211,346 granted Oct. 12, 1965.
Although this principle works quite well in most instances, particularly where the pump chambers are relatively small, or where a measured does is required, there are situations where it does not operate as well as might be desired. Most importantly, if the operator does not allow the stem to return to its fully outward position, i.e., where he executes short strokes, the inlet valve to the pump chamber will not open to allow it to refill. It must be noted that in such an arrangement the inlet to the pump chamber is not opened until the piston has almost reached its at-rest position. On the other hand, when using a conventional check valve, the pump chamber begins refilling almost immediately upon the beginning of the outward stroke. This allows short strokes. A problem can also occur if the operator, instead of releasing the dispensing stem all at once, lets it slowly come out. This permits leakage of air around the piston and improper refilling.
Accordingly, efforts have been made to provide an improved valve member for a pump of the general type described above which comprises a minimum number of pieces and which is easy to assemble.
Many of these objects are achieved, by the construction of the U.S. Pat. No. 4,230,242. In this patent, the pump includes a valve member having an outer solid portion which projects into an opening below the piston and acts to close off an inlet port to the dispensing stem, and an inner larger section which is hollow on the inside and adapted to receive a biasing spring. This valve member is molded in one piece with a recess formed therein directly outward of the hollow area in the inner portion. The recess is narrowed to a throat at the point where it communicates with the hollowed area, with the throat of a diameter smaller than the rest of the recess and smaller than the diameter of a steel ball which is to be used as the ball check. The recess is maintained in communication with the pump chamber by means of openings which extend through the valve member. With this simple assembly, the valve member operates as a triple seal valve member, the outer part of the valve member acts to seal against the inlet port to the dispensing stem, the inner part of the valve member seals against the throat at the inner end of the pump chamber and the ball check valve acts as a further seal during dispensing.
Furthermore, the use of the valve member in combination with a flexible annular seal results in improved sealing at the inlet of the pump chamber, while still permitting fast refilling by means of the ball check valve. The inner portion of the valve member which is hollowed out to receive a spring can be made so as to form an additional inlet valve or may be manufactured so that it is always in sealing contact with the flexible annular seal.
Despite the advantages offered by the pump construction of U.S. Pat. No. 4,230,242, in some instances, problems result because the area of the point at which the outlet area of the point at which the outlet through the stem was sealed has typically been kept to a minimum. It has generally been thought that this is desirable since it is easier to effectively seal a smaller rather than larger area. What this means is that, the area available for the pressure mechanism to act against the biasing force and open the outlet is not substantially different than the area available immediately after opening. Thus, continued force by the user at about the same level is necessary to keep the pump operating against the spring force over its full stroke. If the user firmly and decisively pushes down on the actuator, a single puff will result. However, if the pressure is applied slowly and not smoothly a series of puffs result and the operator can vary the dose considerably.
With respect to prepressurized pumps which do not utilize ball check valves, one possible solution to this problem is proposed in U.S. Pat. No. 4,735,347. In the pump disclosed in this application, the sealing area at the outlet is increased substantially, e.g. over ten times. This increase in the sealing area has a number of effects. First of all, it reduces the effective piston area. The reduction of effective piston area results in an increased pressure for a given finger force. It also decreases the area of the valve member on which the pressure acts before opening. This, in turn, permits the use of a lighter spring for a given pressure. When the valve does open, the area available for the pressure to act upon is increased substantially. Although, after opening, the pressure will drop somewhat due to the flow, there is a resistance to flow, particularly because of the break-up actuator. The pressure in the chamber, thus, acts on a much greater area, developing a greater force, which acts against the valve member and drives the valve member down against biasing spring which, as noted above, can already be of a smaller force. The result, as far as the finger is concerned, is similar to the result where one is pushing against something and overcomes static friction. It is essentially impossible for the average person to control the resulting finger movement which occurs after having built up force in the finger with the back pressure released to the extent it is. The result is that a full stroke is accomplished immediately with a single puff of finely atomized spray, atomization taking place at a higher pressure than in other pumps.
While increasing the area of the point at which the outlet through the stem is sealed offers the advantage of one-shot dispensing, it also presents a variety of problems when employed in a valve member utilizing a ball check valve such as in U.S. Pat. No. 4,230,242. Specifically, use of a large diameter stem top requires a tight seal between the ball and the recess in which the ball is seated. However, the provision of such a tight seal increases the vacuum created after the product is dispensed from the pump chamber. This vacuum could result in pump lock up wherein the pump stem is unable to return to its outermost position because the spring cannot overcome the locking force of the vacuum. Further, the high pressure build up necessary before the stem moves can create an unnatural feeling for the user since a large force is required to initiate movement.